Birds of a feather

: Everyone I know cuts this phrase short "Birds of a feather flock together as do pigs and swine, rats and mice will have their choice and so shall I have mine."
: Yet after a recent lecture on the history of racism I became very interested in finding the origin of this rhyme.

'Birds of a feather flock together' isn't a shortening of that nursery rhyme version. The longer version came much later. The phrase derives from the earlier still 'birds of a feather will flye together', which is early 17th century. There was no racist element in the original coining.